1. Field of Invention
This invention relates to accessories for a micrometer, specifically to those accessories which are attachable to, and detachable from a conventional outside micrometer.
2. Description of Prior Art
Attachments for a conventional outside micrometer are commonly used in the manufacturing and machining industries. The general function of these attachments is to facilitate accurate measurement taking of specific part or material shapes.
There are two types known to this inventor. Both types modify the interface between the micrometer and the item being measured. The first type mounts directly over the micrometer spindle or anvil measuring faces and is commonly retained to them by a rubber attachment boot or sleeve apparatus. These are commonly known as anvil and spindle attachments. As found, all of these attachments add a length to the anvil or spindle, which must be subtracted from the measurement. None have been found to create a platform, surface, or "table" to support or align the measured item.
The second type consists of specialty micrometers which employ interchangeable spindles or anvils of various configuration. None of them have been found to create a table to support or align the measured item. Micrometer stands might be considered add-on accessories, however they support the micrometer itself, and again do not support or align the measured item.
There are only two micrometer-type measuring tools known to this inventor which do support or align the measured item. One is known as a "wire micrometer". It is a specialty micrometer, not an add-on accessory for a conventional micrometer. The table of a wire micrometer is a non-removable part of the micrometer itself. The table configuration greatly reduces the clearance to measure most common items. There is no clearance loop, or "throat" between the spindle and the anvil, as there is on a conventional micrometer. The inability to measure most common items, and the prohibitive expense of this specialty tool, tends to limit sales to specific industries such as the wire forming industry.
In addition, wire micrometers are not easily held and utilized in one hand. The throat loop of a conventional micrometer is normally grasped between the tip of the pinky finger and the palm of the hand. This allows the micrometer to be positively retained, while the measuring adjustment (barrel rotation) is accomplished with the thumb and index finger. Therefore, the normal operation of a conventional micrometer is one-handed, allowing the other hand to hold the item being measured. Although a wire micrometer may be held in one hand, there is no throat loop to be grasped, thus it may easily be dropped. Another disadvantage of the wire micrometer table is that it is narrow, generally about 13 mm. wide. It is difficult to stabilize many measured items on this small surface area. The normal measuring range is only zero to 13 mm. or less, compared to the conventional micrometer measuring range of zero to 25.4 mm. The table is also not free to rotate about the measurement axis. To measure a stationary item, the wire micrometer itself must be positioned so that the "table" rests flat against the item. This often requires the scale or digital readout to be facing at an angle away from the operator.
The other type of micrometer found to incorporate a table surface on which the measured item may be supported is known as a bench micrometer. A bench micrometer has an integral heavy base. It is not a hand held tool. It is designed to rest stationary on a workbench, therefore the object to be measured is brought to it. The table surface of a bench micrometer is an integral part of the tool, not an attachment. Also as found, the table surface does not have rotational self-aligning capability.
U.S. Pat. No. 5,463,818 to Hughes (1994), and U.S. Pat. No. 5,287,631 to Stade (1991), disclose micrometer-type measuring tools with tables on which to rest the measured item. However, they are also bench type micrometers, not attachments to a conventional micrometer.